Tuesday, December 3, 2019

Merely Possessing a Placebo Analgesic Reduced Pain Intensity: Preliminary Findings from a Randomized Design

Merely Possessing a Placebo Analgesic Reduced Pain Intensity: Preliminary Findings from a Randomized Design. Victoria Wai-lan Yeung, Andrew Geers, Simon Man-chun Kam. Current Psychology, February 2019, Volume 38, Issue 1, pp 194–203. https://link.springer.com/article/10.1007/s12144-017-9601-0

Abstract: An experiment was conducted to examine whether the mere possession of a placebo analgesic cream would affect perceived pain intensity in a laboratory pain-perception test. Healthy participants read a medical explanation of pain aimed at inducing a desire to seek pain relief and then were informed that a placebo cream was an effective analgesic drug. Half of the participants were randomly assigned to receive the cream as an unexpected gift, whereas the other half did not receive the cream. Subsequently, all participants performed the cold-pressor task. We found that participants who received the cream but did not use it reported lower levels of pain intensity during the cold-pressor task than those who did not receive the cream. Our findings constitute initial evidence that simply possessing a placebo analgesic can reduce pain intensity. The study represents the first attempt to investigate the role of mere possession in understanding placebo analgesia. Possible mechanisms and future directions are discussed.

Keywords: Placebo effect Mere possession Cold pressor Placebo analgesia Pain

Past research has demonstrated that placebo analgesics can increase pain relief. The primary focus was on pain relief that occurred following the use of the placebo-analgesic treatment. We tested the novel hypothesis that merely possessing a placebo analgesic can boost pain relief. Consistent with this hypothesis, participants who received but did not use what they were told was a placebo-analgesic cream reported lower levels of pain intensity in a cold-pressor test than did participants who did not possess the cream. To our knowledge, the present data are the first to extend research on the mere-possession phenomenon (Beggan 1992) to the realm of placebo analgesia.

Traditional placebo studies have included both possessing and consuming: Participants first possess an inert object, then they consume or use it and report diminished pain as a consequence (Atlas et al. 2009; de la Fuente-Fernández et al. 2001; Price et al. 2008; Vase et al. 2003). The current study provided initial evidence that consuming or using the placebo analgesia is unnecessary for the effect. However, it remains possible that the effect would be enhanced were possession to be accompanied by consumption or use. This and related hypotheses could be tested in future studies.

In the current experiment, we measured several different variables (fear of pain, dispositional optimism, desire for control, suggestibility, and trait anxiety) that could be considered as potential moderators of the observed placebo-analgesia effect. However, none of them proved significant. Although we remain unsure of the processes responsible for the mere possession effect we observed, a previously offered account may be applicable. Specifically, participants’ pain reduction may have been induced by a positive expectation of pain relief that was mediated by an elevated perception of self efficacy in coping with pain (see Peck and Coleman 1991; Spanos et al. 1989). To directly test this possibility in further research, it would be important to measure participants’ self-perceived analgesic efficacy in relation to the mere-possession effect.

It is possible that the mere possession of what participants were told was an analgesic cream induced a positive affect through reception of a free gift. The affect may have influenced participants’ perceived pain intensity. In order to test this possibility, we looked more closely at an item in the State-Anxiety Subscale (Spielberger et al. 1983), specifically, BI feel happy^. Participants in the mere-possession condition did not feel happier (M = 2.47, SD = .96) than those in the nopossession condition (M = 2.80, SD = .70), t(37) = 1.22, p = .23, d = .38, CI95% = [−0.24, 1.00]. Nevertheless, since the participants completed the State-Anxiety Subscale after they received the cream and following the pain-perception test, in order to strictly delineate the effect of affect from other factors, future research should measure participants’ mood after they receive the cream and prior to the pain-perception test. In our study, participants’ pain reduction could not be attributed to the mere-exposure effect because participants in both conditions were initially exposed to the sample of the cream simultaneously. The only difference between the two conditions was that participants in the mere-possession condition were subsequently granted ownership of the sample cream, but participants in the no-possession condition did not.

A significant group difference in pain perception appeared in the analysis of the MPQ results but not those from the VAS. There are at least two possible reasons for this outcome. First, prior researchers had demonstrated that the VAS is sensitive to changes in perceived pain when participants are asked to continuously report their pain intensity (Joyce et al. 1975; Schafer et al. 2015).

In our study, participants reported their pain intensity only once. Whether a significant group difference would be observed if the VAS was to be administered several times within the 1-min immersion duration is presently unknown. Second, it should be noted that VAS may not be sensitive to Asians’ pain perception (Yokobe et al. 2014). No similar observation has been made about results from the use of the MPQ.

Our findings add to the placebo-analgesia literature by indicating potential directions for further research, including limitations of our study that will need to be considered. First, we induced participants to seek the reduction of pain and to anticipate the effectiveness of the placebo. Doing so may have optimized the incidence of the mere-possession effect. Second, although our data demonstrated that the effect we observed was not due to a positive feeling in response to receiving a free gift, future studies might involve a control condition in which the gift is not purported to relieve pain. Third, our participants were healthy university students of Chinese ethnicity. Prior research has shown that cultural background influences pain perception (Callister 2003; Campbell and Edwards 2012). Future researchers may extend the ethnic and cultural range of the participants in an effort to generalize the current findings. Moreover, it seems critical to conduct future research with clinical patients who are in demonstrable pain. Lastly, it is unclear whether the mere-possession effect extends to other types of pain-induction tasks, such as those involving heat (e.g., Mitchell et al. 2004; Duschek et al. 2009) or loud noise (e.g., Brown et al. 2015; Rose et al. 2014).

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